Instructions for php multi-process execution tasks

This article mainly introduces the instructions on PHP multi-process execution tasks. It has a certain reference value. Now I share it with you. Friends in need can refer to it.

Requirements

Yes A specified number of multiple tasks are executed concurrently, and the number of processes is controlled.

Processes & Threads:

The processes are independent of each other and do not affect each other.

Code example:

<?php

$task = 0; //任务id
$taskNum = 10; //任务总数
$processNumLimit = 2; //子进程总量限制

while(true){
   //产生分支
   $processid = pcntl_fork();

   //创建子进程失败
   if( $processid == -1 ){
       echo "create process error！\n";
       exit(1);
   }
   //主进程，获得子进程pid
   elseif($processid){
       $task++; //下一个任务

       $currentProcessid = posix_getpid(); //当前进程的Id
       $parentProcessid = posix_getppid(); // 父级进程的ID
       $phpProcessid = getmypid(); //当前php进程的id
       echo "task:",$task,"\tprocessid:",$processid,"\tcurrentProcessid:",$currentProcessid,"\tparentProcessid:",$parentProcessid,"\tphpProcessid:",$phpProcessid,"\n";

       //控制进程数
       if($task >= $processNumLimit) {
           echo "wait chl start！\n";
           $exitid = pcntl_wait($status); //等待退出
           echo "wait chl end！extid:",$exitid,"\tstatus:",$status,"\n";
       }
       
       //任务总量控制
       if($task >= $taskNum) {
           echo "taskNum enough！\n";
           break;
       }
   }
   //processid=0为新创建的进程
   else{
       //模拟不同任务的不同执行时长
       $sleep = rand(1, 5);

       $currentProcessid = posix_getpid(); //当前进程的Id
       $parentProcessid = posix_getppid(); // 父级进程的ID
       $phpProcessid = getmypid(); //当前php进程的id
       echo "task:",$task,"\tprocessid:",$processid,"\tcurrentProcessid:",$currentProcessid,"\tparentProcessid:",$parentProcessid,"\tphpProcessid:",$phpProcessid,"\tsleep:",$sleep,"\tbegin!\n";

       sleep($sleep);

       echo "task:",$task,"\tprocessid:",$processid,"\tcurrentProcessid:",$currentProcessid,"\tparentProcessid:",$parentProcessid,"\tphpProcessid:",$phpProcessid,"\tsleep:",$sleep,"\tend!\n";
       
       exit(0); //子进程执行完后退出，防止进入循环创建子进程
   }
}

Result of execution:

task:1    processid:32225    currentProcessid:32224    parentProcessid:15053    phpProcessid:32224
task:0    processid:0    currentProcessid:32225    parentProcessid:32224    phpProcessid:32225    sleep:5    begin!
task:2    processid:32226    currentProcessid:32224    parentProcessid:15053    phpProcessid:32224
wait chl start！
task:1    processid:0    currentProcessid:32226    parentProcessid:32224    phpProcessid:32226    sleep:2    begin!
task:1    processid:0    currentProcessid:32226    parentProcessid:32224    phpProcessid:32226    sleep:2    end!
wait chl end！extid:32226    status:0
task:3    processid:32228    currentProcessid:32224    parentProcessid:15053    phpProcessid:32224
wait chl start！
task:2    processid:0    currentProcessid:32228    parentProcessid:32224    phpProcessid:32228    sleep:1    begin!
task:2    processid:0    currentProcessid:32228    parentProcessid:32224    phpProcessid:32228    sleep:1    end!
wait chl end！extid:32228    status:0
task:4    processid:32229    currentProcessid:32224    parentProcessid:15053    phpProcessid:32224
wait chl start！
task:3    processid:0    currentProcessid:32229    parentProcessid:32224    phpProcessid:32229    sleep:2    begin!
task:0    processid:0    currentProcessid:32225    parentProcessid:32224    phpProcessid:32225    sleep:5    end!
wait chl end！extid:32225    status:0
task:5    processid:32270    currentProcessid:32224    parentProcessid:15053    phpProcessid:32224
wait chl start！
task:4    processid:0    currentProcessid:32270    parentProcessid:32224    phpProcessid:32270    sleep:1    begin!
task:3    processid:0    currentProcessid:32229    parentProcessid:32224    phpProcessid:32229    sleep:2    end!
wait chl end！extid:32229    status:0
task:6    processid:32271    currentProcessid:32224    parentProcessid:15053    phpProcessid:32224
wait chl start！
task:5    processid:0    currentProcessid:32271    parentProcessid:32224    phpProcessid:32271    sleep:4    begin!
task:4    processid:0    currentProcessid:32270    parentProcessid:32224    phpProcessid:32270    sleep:1    end!
wait chl end！extid:32270    status:0
task:7    processid:32273    currentProcessid:32224    parentProcessid:15053    phpProcessid:32224
wait chl start！
task:6    processid:0    currentProcessid:32273    parentProcessid:32224    phpProcessid:32273    sleep:1    begin!
task:6    processid:0    currentProcessid:32273    parentProcessid:32224    phpProcessid:32273    sleep:1    end!
wait chl end！extid:32273    status:0
task:8    processid:32274    currentProcessid:32224    parentProcessid:15053    phpProcessid:32224
wait chl start！
task:7    processid:0    currentProcessid:32274    parentProcessid:32224    phpProcessid:32274    sleep:2    begin!
task:5    processid:0    currentProcessid:32271    parentProcessid:32224    phpProcessid:32271    sleep:4    end!
task:7    processid:0    currentProcessid:32274    parentProcessid:32224    phpProcessid:32274    sleep:2    end!
wait chl end！extid:32274    status:0
task:9    processid:32277    currentProcessid:32224    parentProcessid:15053    phpProcessid:32224
wait chl start！
wait chl end！extid:32271    status:0
task:8    processid:0    currentProcessid:32277    parentProcessid:32224    phpProcessid:32277    sleep:2    begin!
task:10    processid:32278    currentProcessid:32224    parentProcessid:15053    phpProcessid:32224
wait chl start！
task:9    processid:0    currentProcessid:32278    parentProcessid:32224    phpProcessid:32278    sleep:2    begin!
task:8    processid:0    currentProcessid:32277    parentProcessid:32224    phpProcessid:32277    sleep:2    end!
task:9    processid:0    currentProcessid:32278    parentProcessid:32224    phpProcessid:32278    sleep:2    end!
wait chl end！extid:32277    status:0
taskNum enough

Execution analysis:

1. After pcntl_fork creates a child process, The child process executes the function code, and the parent process continues to increment the task id and create the next task process;

2. Wait through pcntl_wait for a child process to finish executing and exit, then create a new process to achieve the total number of processes Control;

3. After the main process completes creation, exit the loop through break. There may be child processes continuing to execute at this time.

Related functions:

pcntl_fork

Generate a branch (child process) at the current position of the current process. On success, the PID of the generated child process is returned in the parent process execution thread, and 0 is returned in the child process execution thread. On failure, -1 is returned in the parent process context, the child process is not created, and a PHP error is raised.

pcntl_wait

Wait or return the child process status of fork. The wait function scrapes the execution of the current process until a child process exits or receives a signal that requires interrupting the current process or calling a signal handling function. If a child process has exited when this function is called (commonly known as a zombie process), this function returns immediately. All system resources used by the child process will be released.

Others:

1. Problems with zombie processes and orphan processes

Some zombie processes obtain status and release resources by pcntl_wait, and processes that have not been taken over become Orphan process. The orphan process is adopted by the init process to complete wait's status acquisition and resource release.

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